Arjuna asks to see the whole form, and is given it. A thousand suns rising at once (11.12). Every god and every kind of being inside one body. Then the fanged mouths, and the warriors of both armies pouring into them like rivers reaching the sea, like moths into a flame (11.28–30).
And then he asks it to stop. Gladdened am I to have seen what was never seen before, yet my mind is shaken with fear. Show me, O God, that other form (11.45–46). The most quoted vision in the song ends with the one who begged for it begging for the ordinary face back.
It would be easy to read that as nerve failing. The text does not read it that way. The gentle form is restored without a word of reproach — let there be no fear in you, no bewilderment (11.49) — and the chapter's own summary is that this form is not reached by study, or sacrifice, or austerity, but by undivided love alone (11.54). The vision was shown by grace and by no other means (11.47); it was never a rung anyone climbed to.
That reframes what it was for. Not a reward for practice, and not a state to be maintained — it was shown once, and then withdrawn, because what a person can actually live beside is a face and not a furnace. The chapter gives the seer the terrifying scale so that he knows what stands behind the familiar form, and then hands the familiar form back so that he can get up off the floor and work.
The vision is in the book so that nobody mistakes the friend in the chariot for something small. It is over by the end of the chapter so that the friend in the chariot is who you actually have.